1. The Field of the Invention
The present invention is directed to the field of emergency medicine. More particularly, the present invention is directed to an emergency medication pump system designed to automatically calculate dosages and administer selected medications to a patient based on minimal input (e.g., the patient's weight).
2. The Relevant Technology
The intravenous infusion of various types of medications is an important part of the treatment of many patients. This is particularly true in an emergency situation where a patient may require a series of life-saving injections of a variety of medications. Often these injections must be given in rapid succession and according to a particular protocol. Delays and/or deviations from protocol can be life-threatening. Injections of medications may begin when a patient is first contacted by emergency medical technicians or when the patient arrives in the emergency department of a hospital. Regardless, when a patient is first administered to by emergency medical personnel, the personnel will rapidly assess the patient's clinical situation and, if appropriate, they may immediately begin giving intravenous medications.
For example, if an unconscious patient arrives in the emergency department with severe breathing difficulties, it is typically necessary to insert a breathing tube into the patient's airway for ventilation and oxygenation. This process is called emergency endotracheal intubation. Intubation, however, must be performed with care because of the patient's innate gag reflex. For example, if the breathing tube is inserted into the patient's airway without pretreating the patient with proper medications there is a considerable risk that the patient may vomit and choke.
Typically, emergency endotracheal intubation is performed in conjunction with a procedure called rapid sequence intubation (“RSI”). RSI is the process of inducing unconsciousness and motor paralysis prior to emergency endotracheal intubation. When a patient needing intubation arrives in the emergency department, the team of nurses and physicians immediately begin giving intravenous fluids, begin oxygen by bag mask ventilation, and arrange equipment and medications to perform RSI. Typical dosages are based on an estimate of the patient's weight and on the specific clinical situation. Of course, those of skill in the art will recognize that the term “patient weight” as used herein refers to not necessarily the actual weight of the patient, but an ideal body weight, as excess body fat is typically not accounted for when determining dosing of most medications (e.g., a typical adult patient may have a “weight” of about 70 kg).
A patient needing RSI will receive a potent induction agent to induce anesthesia, followed by a rapid acting neuromuscular blocking agent to induce partial paralysis. A typical induction agent is Etomidate, given at a rate of 0.3 mg/kg, and a typical blocking agent succinylcholine, given at a rate of 1.5 mg/kg. In some situations the patient may also receive so-called “pre-medications” prior to administering the induction agent and the blocking agent. These pre-medications may be administered to protect the central nervous system in patients who are being intubated where a brain injury, such as an intracranial hemorrhage, is suspected. For example, a patient may receive Fentanyl at a rate of 3 μg/kg, Lidocaine at a rate of 1 mg/kg, and/or a defasciculating dose of Vecuronium.
Another example of an emergency medical procedure involving rapid and successive injection of multiple medications is advanced cardiac life support (“ACLS”). ACLS is a comprehensive approach to the resuscitation and/or treatment of a patient with a serious heart condition. Typical medications used in ACLS include epinephrine, atropine, dopamine, lidocaine, and anti-arrhythmics. ACLS is used by emergency medical personnel to restore normal cardiac function to patients in cases of cardiac arrest. Cardiac arrest is a general term that includes asystole, bradycardia, ventricular tachycardia, and pulseless electrical activity (PEA).
ACLS is used in most cases of general cardiac arrest; however, the precise treatment that a patient receives is a function of the patient's condition. For example, in a case of asystole where the patient has no pulse and there is an absence of electrical activity in the heart, emergency medical personnel will perform cardiopulmonary resuscitation along with administering injections of epinephrine at a rate of 0.01-0.03 mg/kg followed by atropine at a rate of 0.02 mg/kg. In a case of bradycardia where the patient's heart rate is slower than expected for a given situation, emergency medical personnel will administer injections of atropine at a rate of 0.02 mg/kg followed by epinephrine at a rate of 0.01-0.03 mg/kg along with electrical stimulation of the heart. Other medications may be given in different situations. In addition, patients undergoing ACLS may also be candidates for RSI.
A third example of an emergency medical procedure involving rapid and successive injection of multiple medications is procedural sedation. Procedural sedation is a clinical technique that creates a decreased level of awareness for a patient during a potentially painful and/or frightening procedure yet maintains protective airway reflexes and adequate spontaneous ventilation. Agents used in procedural sedation are of three general classes: sedatives, analgesics, and induction agents in reduced amounts. For example, if a patient comes into the emergency department with a dislocated shoulder, it is generally necessary to sedate the patient in order to return the head of the humerus bone to its place in the shoulder joint in a procedure called “reduction” or “reducing the shoulder.” Shoulder dislocation causes the patient great pain, and the subsequent reduction can be excruciating in and of itself. As a result of the muscle tension that naturally results from the pain of a dislocated shoulder, great strength is required to reduce the shoulder if the patient is not relaxed and sedated. In contrast, under sedation the patient is much more comfortable and the reduction can be performed with a minimum of effort. In a typical protocol, the patient is preoxygenated and intravenous Propofol is administered in 20 mg increments up to a maximum dosage of about 1.5-3.0 mg/kg. The Propofol injections are repeated until the patient is relaxed and the shoulder can easily be reduced back into place by the physician.
A common thread that joins RSI, ACLS, procedural sedation, and other emergency procedures under current practice is that each medication administered to a patient requires a separate calculation to arrive at a correct dosage based mainly or exclusively on the patient's weight. Time is of the essence in emergency medicine, and these calculations cost valuable time. Currently the solution to this need is to have the multiple medications necessary assembled in a single box which is carried to the bedside of the patient in distress. Some facilities place a locked box in the trauma/resuscitation rooms that are stocked with these medications, and the box is opened as the patient arrives. The physician calculates the amount of each medication to be administered. The process is repeated for as many as 5 (or more) medications. The physician gives orders to a nurse to draw into separate syringes the medications to be utilized based on the patient's weight and clinical situation. Valuable time is spent drawing each medication into a separate syringe. If the syringes are placed at the patient's bedside, they can be indistinguishable from the other syringes now full of clear liquid, making a mix-up possible.
At the physician's order, the medications are injected into the IV rapidly in a set order. More time is expended as each syringe is injected serially into the IV port. The nurse handling the medications is typically a more senior, experienced member of the team. Larger facilities may even call a pharmacist to the Emergency Department to prepare these medications. The team waits for this process to be completed when time is of the essence. The mental concentration required for calculating, confirming accuracy, and overseeing administration of these medications distracts or delays the physician and other members of the team from performing other life saving interventions. As noted, the more experienced members of the medical team are involved in these crucial steps. Freeing them to focus their efforts elsewhere would be invaluable.
In addition to wasting valuable time and resources, the current procedure increases the risk of errors in dosing, and presents a risk of accidental needle sticks to the emergency medical personnel due to the rush in providing treatment to the patient in the emergency situation. Moreover, most medications are clear liquids and they cannot easily be differentiated once they are drawn into a syringe. Because of this, medications can be given in the wrong sequence if they are drawn into a series of syringes and laid out for injection. Further, because of the rush that is natural to an emergency situation, records of which medications were administered, when they were administered, and in what amounts may not be properly kept or correctly remembered afterwards.
Accordingly, there are a number of difficulties associated with emergency medicine where it is necessary to rapidly deliver multiple injections of multiple medications. In particular, there are a number of difficulties present in terms of locating the appropriate medications, calculating correct dosages, drawing up the medications into a series of syringes, and administering them to the patient in the proper sequence. Therefore, it would be advantageous to provide a system where the medications for a number of emergency procedures are preassembled where the various medications can be administered without having to manually calculate dosage amounts for each, and where they can be rapidly administered in the proper sequence, all while minimizing the disadvantages described above.